West Nile Virus

West Nile Virus

In 1999, West Nile virus (WNV) was first documented in the United States during an outbreak of meningitis and encephalitis in NYC. Since its introduction, it became established throughout much of the United States, and has spread into Canada and Mexico.


WNV is a mosquito-borne disease that is spread by the bite of an infected mosquito. An estimated 80% of people infected with the virus show no symptoms. Approximately 20% of infections cause a clinical presentation known as West Nile Virus fever, which is characterized by an acute onset of fever, and can be accompanied by, but not limited to, headache, muscle aches, fatigue and joint pain.

One in 150 people infected with WNV will go on to develop severe symptoms, which can include fever, headache, stiff neck, disorientation or confusion, vision loss, seizures, and paralysis. In some cases, the neurological effects of WNV infection can be permanent. There is no treatment available for WNV. Treatment for severe cases consists of supportive care. The best defense against WNV is to protect yourself from biting mosquitoes and to eliminate mosquito breeding areas.

How to eliminate mosquito breeding areas:

  • Turn over or remove containers in your yard where rainwater collects, such as potted plant trays, buckets, or toys.
  • Empty bird baths once a week.
  • Remove old tires from your yard.
  • Clean roof gutters and downspout screens.
  • Elimnate standing water on flat roofs, boats, and tarps.
  • Clear obstructions in ditches so they flow and drain. Fill in puddles with soil, or a mixture of sand and gravel, or dig drainage ditches to drain puddles.
  • If puddles or ditches cannot be drained or filled in, treat standing water with mosquito larvicide’s (dunks or granules) that can be purchased at any hardware store.

How to protect yourself from mosquitoes that bite:

  • Wear long, loose and light-colored clothing.
  • Use insect repellent products with no more than 50% DEET for adults and less than 30% for children
  • Follow label instructions when using insect repellents.


Prevent West Nile Virus Poster
Prevent West Nile Virus Poster

West Nile Virus Fact Sheet

Arbovirus Test Results by Year

Arboviral Activity Maps by Year

Birds Reported and Tested for WNV

How to Eliminate Standing Water

FAQ About Mosquitoes